from what I remember, he didn't properly apologize to the mcs on screen but he stopped being shitty somewhere near the ending because of sunbae. They explained the reason he's the way he is (a really abusive and homophobic dad he's stuck with) and the kid gets beat up on a daily basis. Sunbae said "he has never been shown love how would he know how to give it?" and that changed my whole perspective on him. He definitely changed a lot after the timeskip too since he's in Seoul now, away from his abusive dad!
Ikr.
He even choose to go to jail to make sure the other 3 won't get complicated.
And I suspect the one who trampled and throw rubbish into Jiwon house is Sunny's bad father.
people are talking about how shitty and evil Sunny was but didn't he have like one of the best redemption arcs? I read this in february but I do remember him being like all good now no?